Chemical and Structural Modifications of Nanoporous Alumina and Its Optical Properties

Structural and Fluorescence Studies of Polycrystalline α‐Al2O3 Obtained From Sulfuric Acid Anodic Alumina

“…Various metal oxides also showed the same photoluminescence of OH‐related centers in oxidized nanocrystalline and porous silicon, hydrated alumina oxide, hydrated lead oxide and zinc oxide . In as‐anodized anodic alumina and in α‐Al 2 O 3 , fluorescence at about 400–440 and 500 nm can be also attributed to F and F 2 centers, respectively …”

“…G.S Huang et al found that fluorescence at about 465 nm of porous anodic alumina formed in sulfuric acid is caused by the oxygen vacancies in the membrane and another blue emission band in the 400–440 nm region is attributed to the optical transition in the isolated OH groups at the surface . Other scientists found that fluorescence band in the 400–440 nm is typical for embedded impurities such as malonate and tartarate ions . Various metal oxides also showed the same photoluminescence of OH‐related centers in oxidized nanocrystalline and porous silicon, hydrated alumina oxide, hydrated lead oxide and zinc oxide .…”

“…[14] Other scientists found that fluorescence band in the 400-440 nm is typical for embedded impurities such as malonate and tartarate ions. [15][16][17][18] Various metal oxides also showed the same photoluminescence of OH-related centers in oxidized nanocrystalline and porous silicon, hydrated alumina oxide, hydrated lead oxide and zinc oxide. [19] In as-anodized anodic alumina and in α-Al 2 O 3 , fluorescence at about 400-440 and 500 nm can be also attributed to F and F 2 centers, respectively.…”

“…[19] In as-anodized anodic alumina and in α-Al 2 O 3 , fluorescence at about 400-440 and 500 nm can be also attributed to F and F 2 centers, respectively. [12,17,[20][21][22][23] In the present study, we obtained robust α-Al 2 O 3 samples with size of 2.6 cm 2 and thickness of 144 mm by the heat treatment at 1400 C of free-standing sulfuric anodic alumina specimens and investigated their physical, chemical and fluorescence properties.…”

A 1D conical nanotubular TiO2/CdS heterostructure with superior photon-to-electron conversion

“…Similar reflection, scattering and transmittance features were described already for porous alumina. 74 The penetration depth of light in the CdS sub bandgap tail spectral region is rather large (about 1 μm) and the TiO 2 nanotubes are optically transparent for these wavelengths, therefore it is easy to imagine a huge number of successive transmissions of light through the CdS/TiO 2 nanotube walls before the photons escape from the TiO 2 nanotube layer as diffuse reflected light or become absorbed inside the CdS/TiO 2 nanotube layers. In fact, there are mainly these multiple transmissions, each coupled with small, but not negligible light absorption in the CdS Urbach tail, which results in an effective band gap lowering of the CdS/TiO 2 nanotube layer ( Fig.…”